Control method for a direct-coupling mechanism in hydraulic power transmission means of an automatic transmission for automotive vehicles

Abstract

A method of controlling a direct-coupling mechanism of hydraulic power transmission device of an automatic transmission for an automotive vehicle, wherein the transmission capacity of the direct-coupling mechanism is controlled such that the valve of a predetermined parameter indicative of an amount of relative slip between input and output members of the hydraulic power transmission device which are mechanically engaged with each other by the direct-coupling mechanism lies within a predetermined reference range. The predetermined parameter value is detected and the detected value is compared with the predetermined reference range. A desired value of the predetermined reference range and a predetermined period of time are determined on the basis of the comparison result. The transmission capacity is controlled to the determined desired value for the determined predetermined period of time. The transmission capacity is maintained so long as the detected predetermined parameter value lies within the predetermined reference range. At least first and second transmission capacity increasing regions are provided which correspond to larger values of the amount of relative slip than that the predetermined reference range corresponds to, wherein the first region is closer to the predetermined reference range than the second region is. A rate of increase of the transmission capacity in the first region is set to a value smaller than that in the second region. A fine-control region is provided adjacent at least one of extreme limits of the predetermined reference range, wherein the transmission capacity is finely adjusted toward the predetermined reference range.

What is claimed is: 
     
       1. A method of controlling a direct-coupling mechanism of hydraulic power transmission means having an input member and an output member, of an automatic transmission for an automotive vehicle, said direct-coupling mechanism being operable to mechanically engage and disengage said input member and said output member with and from each other, wherein a transmission capacity of said direct-coupling mechanism is controlled such that the value of a predetermined parameter indicative of an amount of relative slip between said input member and said output member lies within a predetermined reference range, the method comprising the steps of: (1) detecting the value of said predetermined parameter; (2) comparing the detected value of said predetermined parameter with said predetermined reference range; (3) determining a desired value of said transmission capacity and a predetermined period of time on the basis of the result of said comparison such that as the detected value of said predetermined parameter approaches said predetermined reference range, a rate of change in said transmission capacity is decreased; and (4) controlling the transmission capacity to the determined desired value thereof for the determined predetermined period of time. 
     
     
       2. A method as claimed in claim 1, wherein the determined desired value of the transmission capacity is maintained so long as the detected value of said predetermined parameter lies within said predetermined reference range. 
     
     
       3. A method as claimed in claim 1, including providing at least first and second transmission capacity increasing regions corresponding to larger values of said amount of relative slip than said predetermined reference range, wherein the difference between the value of said predetermined parameter falling within said first transmission capacity increasing region and said predetermined reference range is smaller than the difference between the value of said predetermined parameter falling within said second transmission capacity increasing region and said predetermined reference range, and setting a rate of increase of the transmission capacity in said first transmission capacity increasing region to a value smaller than that in said second transmission capacity increasing region. 
     
     
       4. A method as claimed in claim 3, wherein said predetermined period of time in said first transmission capacity increasing region is set to a value larger than that in said second transmission capacity increasing region. 
     
     
       5. A method as claimed in claim 3, wherein said transmission capacity is increased in said first transmission capacity increasing region by an increment smaller than in said second transmission capacity increasing region. 
     
     
       6. A method as claimed in claim 1, including providing a fine-control region adjacent at least one of extreme limits of said predetermined reference range, wherein the transmission capacity is finely controlled toward said predetermined reference range. 
     
     
       7. A method as claimed in claim 1, including providing a fine-control region adjacent one of extreme limits of said predetermined reference range, wherein the transmission capacity is finely controlled so as to decrease toward said predetermined reference range. 
     
     
       8. A method as claimed in claim 7, wherein when the value of said predetermined parameter enters said fine-control region from said predetermined reference range and then returns to the latter, the determined desired value of the transmission capacity immediately after the value of the predetermined parameter returns to said predetermined reference range is set to a value smaller than that immediately before the predetermined parameter value enters said fine-control region. 
     
     
       9. A method as claimed in claim 8, wherein when the predetermined parameter value returns to said predetermined reference range the desired value of the transmission capacity in said predetermined reference range is determined in dependence on a manner of change of the predetermined parameter value occurring in said fine-control region immediately before the predetermined parameter value returns to said predetermined reference range. 
     
     
       10. A method as claimed in claim 9, wherein when the predetermined parameter value returns to said predetermined reference range the desired value of the transmission capacity in said predetermined reference range is set to a value corresponding to a period of time for which the predetermined parameter value has stayed in said fine-control region immediately before the predetermined parameter value returns to said predetermined reference range. 
     
     
       11. A method as claimed in claim 7, wherein when the predetermined parameter value enters said fine-control region from said predetermined reference range before the predetermined period of time determined in said predetermined reference range elapses, the predetermined period of time and the desired value of the transmission capacity are set to respective new values immediately upon the entrance of the predetermined parameter value to the fine-control region. 
     
     
       12. A method as claimed in claim 11, wherein when the predetermined parameter value returns to said predetermined reference range from said fine control region before the predetermined period of time set to said new value, the predetermined period of time and the desired value of the transmission capacity are set to respective new values immediately upon the return of the predetermined parameter value to the predetermined reference range. 
     
     
       13. A method as claimed in any of claims 1-12 wherein the predetermined parameter is the ratio in rotational speed between said input member and said output member of said hydraulic power transmission means. 
     
     
       14. A method as claimed in any of claims 1-12 wherein the predetermined parameter is the difference in rotational speed between said input member and said output member of said hydraulic power transmission means.